In the following description, a femtocell is schematically explained.
First of all, ‘femto’ indicates a very small unit of 10 to 15. According to the meaning, a femtocell means a ultra-small/low power, home/business indoor base station. The femtocell is used in a meaning similar to that of a picocell but is used in a meaning of a further advanced function. The femtocell is a small cellular base station connected to a wideband router and is able to connect speech and data of the 3G system as well as the conventional 2G system to a backbone network of a mobile communication service provider through DSL link or the like.
The femtocell provides the following advantages.
First of all, many attentions are paid to the recent report saying that a femtocell accelerates the 3G propagation and triggers of extending indoor coverage. It is expected that the number femtocell terminal users will be incremented up to 102,000,000 and that the number of installed access points (AP) will reach about 32,000,000. And, Stewart Callow, first analyst of ABI Research said, “In aspect of technology, the indoor coverage reinforcement of technology such as W-CDMA, HSPDA, EVDO and the like plays a very important role in providing service.” And, Stewart Callow also said, “Femtocell performs routing on traffics through IP network to considerably reinforce network quality and capability. Simultaneously, OPEX invested to backhaul dedicated lines by mobile carriers is reduced to provide great benefits in strategic and economic aspects.”
The femtocell is able to improve cell coverage and is also able to enhance a quality of voice service. The mobile carriers expect that subscribers will be completely adaptable to 3G by providing data services via femtocells. The femtocell can be called a femto base station (hereinafter abbreviated FBS) or a femto base transceiver station (hereinafter abbreviated BTS).
In summary, the femtocell provides the following advantages.
1. Cell coverage improvement
2. Infrastructure cost decrease
3. New service offering
4. FMC (fixed mobile convergence) acceleration
At least one femtocell is grouped per specific service or region to construct a femtocell group. For instance, a femtocell group granting an access to a specific mobile station only can be called a closed subscriber group (hereinafter abbreviated CSG). A femto base station (FBS) checks a CSG ID of a mobile station and is then able to grant an access to a mobile station having subscribed to a CGS only.
FIG. 1 is a diagram for an example of a network structure including a femto base station (FBS) according to a related art.
First of all, a femto base station is an entity newly added to a conventional network. As the femto base station is used, there are some addable or modifiable matters for an overall network structure. The femto base station directly accesses Internet and is then able to perform almost every function of a base station. Therefore, the femto base station is able to perform almost every function of a general macro base station. Moreover, the femto base station receives data from a general macro base station and is then able to play a role in relaying the received data to a mobile station.
FIG. 1 shows that a femto network gateway (FNG) is added to a conventional network structure. The FNG is able to communicate with an ASN (access service network) gateway and a CSN (connectivity service network). The FNG uses an Rx interface to communicate with the ASN and is also able to use an Ry interface to communicate with the CSN.
The femto base station directly access TCP/IP interne network and is then able to receive a service from the CSN via the FNG. A mobile station connected to the femto base station is able to receive a service of such function as authentication, IMS (IP multimedia subsystem) and the like from the FNG or CSN.
The femto base station is connected to a base station via R1 interface. This indicates that the femto base station is able to receive a downlink (DL) channel of a macro base station. And, the femto base station is able to transmit a control signal to the macro base station.